The disclosure of Japanese Patent Application No. 2001-106165 filed on Apr. 4, 2001, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
1. Field of Invention
The present invention relates to an apparatus and a method for diagnosing an engine system, and more particularly to diagnosing apparatus and method for detecting or monitoring warm-up states of specific portions of an engine system equipped with a heat accumulating device for storing a heating medium or heat carrier for warming up an engine, at least upon starting of the engine in a cold state. The apparatus and method for diagnosing the engine system includes determining whether the diagnosis of the engine system is performed on the basis of the stored engine-water temperature data.
2. Description of Related Art
One conventional type of engine system employs an evaporative purge system wherein fuel vapor or fumes produced in a fuel tank is/are collected in a canister, and the canister is purged to discharge the collected fuel vapor into an intake passage, as needed.
Such an evaporative purge system generally includes a canister for collecting the fuel vapor produced in the fuel tank, a vapor passage for communication between the fuel tank and the canister, and a purge passage for communication between the canister and an intake passage of the engine. In this evaporative purge system, the purge passage is provided with a purge control valve operable between an open state and a closed state thereof, and the canister is provided with an atmosphere inlet valve operable to introduce the atmosphere into the canister.
For such an evaporative purge system as described above, there is known a diagnosing apparatus arranged to diagnose the system to detect a leakage flow of the fuel vapor out of an evaporative space which consists of interior spaces of the fuel tank, canister and vapor passage, and a portion of the purge passage between the canister and the purge control valve. The leakage flow may occur due to holes, cracks, cleavage or any other flaws of a structure which defines the evaporative space. Basically, this diagnosing apparatus is arranged to temporarily hold the atmosphere inlet valve in the closed state and disconnect the purge passage and the intake passage of the engine from each other, for thereby isolating the evaporative space from the engine, and diagnose the system for any abnormality on the basis of a change in the pressure within the thus isolated purge passage.
Namely, a leakage flow of the fuel vapor from the evaporative purge system causes communication of the purge passage with the atmosphere, resulting in a change of the pressure within the evaporative space eventually to the atmospheric level. In the absence of such a leakage flow of the fuel vapor, on the other hand, the pressure of a gaseous fuel within the evaporative space changes eventually to a saturated vapor pressure, so that the pressure within the evaporative space eventually becomes equal to a sum of the saturated vapor pressure and a partial pressure of gases other than the gaseous fuel. The evaporative purge system can be diagnosed on the basis of an amount of change of the pressure within the evaporative space, which varies depending upon whether the system suffers from a leakage flow of the fuel vapor or not.
However, the actual change of the pressure within the evaporative space does not depend solely on the presence or absence of the leakage flow of the fuel vapor, but depends also on various other parameters. For instance, when the temperature within the evaporative space is comparatively high where the evaporative space does not have any flaws, the pressure within the evaporative space tends to be higher than when the temperature is comparatively low. Since the pressure within the evaporative space is influenced by the various parameters, as described above, the pressure level within the evaporative space where the evaporative space suffers from a leakage flow of the fuel vapor is not necessarily appreciably different from that where the passages do not suffer from the leakage flow. For this reason, the conventional diagnosing apparatus does not permit an accurate diagnosis of the evaporative purge system.
One conventionally proposed solution to the drawback described above is to conduct a diagnosis of the evaporative purge system only when the engine is started in a cold state, as disclosed in JP-A-06-81728. That is, the partial pressure of the gaseous fuel within the evaporative space is relatively low when the engine is started in a cold state, so that the influence of the gaseous fuel on the pressure within the evaporative space can be suitably reduced, making it possible to improve the accuracy of the diagnosis.
For promoting the warm-up operation of the engine upon starting of the engine in a cold state, on the other hand, it has been proposed to provide the cooling system of the engine with a heat accumulating device. For example, the heat accumulating device has a passage for circulating a cooling water through the engine, a heat accumulator for storing the cooling water at a high temperature so that the high-temperature water flows through the passage, and an electrically operated pump for feeding the water so as to be circulated between the engine and the heat accumulator. The warm-up operation of the engine upon starting of the engine in the cold state can be promoted by the high-temperature water (heat medium) stored in the heat accumulator.
However, the diagnosing apparatus described above does not permit an accurate diagnosis of the evaporative purge system of the engine provided with the heat accumulating device described above. Described in detail, the warm-up operation of the engine by the heat accumulating device theoretically prevents the diagnosing apparatus from operating to diagnose the evaporative purge system, since the condition for operating the diagnosing apparatus is not satisfied when the engine is in the warmed-up state. Actually, the warm-up operation of the engine by the heat accumulating device does not necessarily heat the interior of the fuel tank to a sufficiently high temperature, so that the evaporative purge system may be diagnosed with high accuracy, in some cases, even where the engine is warmed-up by the heat accumulating device. That is, where the warm-up operation of the engine is effected by the heat accumulating device before starting of the engine, the diagnosing apparatus may erroneously determine that the condition for diagnosing the evaporative purge system is not satisfied, even when the condition is actually satisfied. Thus, there is a risk that the diagnosing apparatus does not permit an accurate diagnosis of the evaporative purge system where the warm-up operation of the engine is effected.
The erroneous determination regarding the condition for operating the diagnosing apparatus may take place not only in the diagnosis of the evaporative purge system, but also in other diagnostic operations in connection with the engine provided with the heat accumulating device to warm-up the engine before starting of the engine, when such diagnostic operations are conducted to check warm-up states of some specific portions of the engine other than the evaporative purge system.
The present invention was made in view of the drawback discussed above. It is therefore a first object of the present invention to provide a diagnosing apparatus for an engine system provided with a heat accumulating device in which the diagnosing apparatus permits an accurate diagnosis of the engine system to detect its warm-up state
A second object of the invention is to provide a method of diagnosing such an engine system in which the method permits an accurate diagnosis of the engine system to detect its warm-up state.
The first object indicated above may be achieved according to a first aspect of the present invention, which provides a diagnosing apparatus for diagnosing an engine system to detect a warm-up state thereof. The engine system is provided with a heat accumulating device arranged to preheat an engine, comprising: a controller that detects a warm-up state of the engine system and stores warm-up data representative of the detected warm-up state in a memory before a warm-up operation of the engine by the heat accumulating device. The controller further performs the diagnosis of the warm-up state on the basis of the warm-up data stored in a memory.
The first object indicated above may be achieved according to another aspect of the present invention, which provides a diagnosing apparatus for diagnosing an engine system and determining whether the diagnosis is performed based on a detected warm-up state thereof. The engine system is provided with a heat accumulating device arranged to preheat an engine, comprising: a controller that detects a warm-up state of the engine system and stores warm-up data representative of the detected warm-up state in a memory before a warm-up operation of the engine by the heat accumulating device. The controller further determines whether the diagnosis of the engine system is performed on the basis of the warmup data stored in the memory.
The second object indicated above may be achieved according to a further aspect of this invention, which provides a method of diagnosing an engine system to detect a warm-up state thereof. The engine system is provided with a heat accumulating device arranged to preheat an engine. The method comprising the steps of: detecting the warm-up state of the engine system before a warm-up operation of said engine by the heat accumulating device; storing warm-up representative of the detected warm-up state in a memory; and performing a diagnosis of the warm-up state on the basis of the warm-up data stored in the memory.
The second object indicated above may be achieved according to a further aspect of the present invention, which provides a method of diagnosing an engine system and determining whether the diagnosis is executed based on a detected warm-up state thereof. The engine system is provided with a heat accumulating device arranged to preheat an engine. The method comprising the steps of: detecting the warm-up state of the engine system before a warm-up operation of said engine by the heat accumulating device; storing warm-up data representative of the detected warm-up state in a memory; and determining whether the diagnosis of the engine system is performed on the basis of the warm-up data stored in the memory.
In the diagnosing apparatus and method according to the present invention, the warm-up state of the engine system is detected before a warm-up operation of the engine by the heat accumulating device and the warm-up data representative of the detected warmup state is stored in the memory. The diagnosis of the warm-up state is performed on the basis of the stored warm-up data. Accordingly, the warm-up state of the engine system, before the warm-up operation of the engine, can be obtained even after the warm-up operation is performed by the heat accumulating device. Thus, the engine system can be diagnosed so as to permit accurate detection of the warm-up state at a desired specific portion or portions of the engine system.